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[88.147.66.140]) by smtp.gmail.com with ESMTPSA id o7sm83472wmc.36.2019.08.07.07.18.06 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 07 Aug 2019 07:18:07 -0700 (PDT) From: Paolo Valente To: Jens Axboe Cc: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, ulf.hansson@linaro.org, linus.walleij@linaro.org, bfq-iosched@googlegroups.com, oleksandr@natalenko.name, pavel@denx.de, Paolo Valente , Douglas Anderson Subject: [PATCH BUGFIX 1/2] block, bfq: reset last_completed_rq_bfqq if the pointed queue is freed Date: Wed, 7 Aug 2019 16:17:53 +0200 Message-Id: <20190807141754.3567-2-paolo.valente@linaro.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190807141754.3567-1-paolo.valente@linaro.org> References: <20190807141754.3567-1-paolo.valente@linaro.org> MIME-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Since commit 13a857a4c4e8 ("block, bfq: detect wakers and unconditionally inject their I/O"), BFQ stores, in a per-device pointer last_completed_rq_bfqq, the last bfq_queue that had an I/O request completed. If some bfq_queue receives new I/O right after the last request of last_completed_rq_bfqq has been completed, then last_completed_rq_bfqq may be a waker bfq_queue. But if the bfq_queue last_completed_rq_bfqq points to is freed, then last_completed_rq_bfqq becomes a dangling reference. This commit resets last_completed_rq_bfqq if the pointed bfq_queue is freed. Fixes: 13a857a4c4e8 ("block, bfq: detect wakers and unconditionally inject their I/O") Reported-by: Douglas Anderson Tested-by: Douglas Anderson Signed-off-by: Paolo Valente --- block/bfq-iosched.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) -- 2.20.1 diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c index 586fcfe227ea..b2009650afc2 100644 --- a/block/bfq-iosched.c +++ b/block/bfq-iosched.c @@ -1924,12 +1924,13 @@ static void bfq_add_request(struct request *rq) * confirmed no later than during the next * I/O-plugging interval for bfqq. */ - if (!bfq_bfqq_has_short_ttime(bfqq) && + if (bfqd->last_completed_rq_bfqq && + !bfq_bfqq_has_short_ttime(bfqq) && ktime_get_ns() - bfqd->last_completion < 200 * NSEC_PER_USEC) { if (bfqd->last_completed_rq_bfqq != bfqq && - bfqd->last_completed_rq_bfqq != - bfqq->waker_bfqq) { + bfqd->last_completed_rq_bfqq != + bfqq->waker_bfqq) { /* * First synchronization detected with * a candidate waker queue, or with a @@ -4808,6 +4809,9 @@ void bfq_put_queue(struct bfq_queue *bfqq) bfqq->bfqd->burst_size--; } + if (bfqq->bfqd && bfqq->bfqd->last_completed_rq_bfqq == bfqq) + bfqq->bfqd->last_completed_rq_bfqq = NULL; + kmem_cache_free(bfq_pool, bfqq); #ifdef CONFIG_BFQ_GROUP_IOSCHED bfqg_and_blkg_put(bfqg);